Sena is always alone at a secret base. One day, a man named Shimu appeared to Sena-chan, who had been asking "Prince, come back soon". Nishimu is just a ro-con, and he cheats on Sena-chan, gets a "first time", and develops Oma-ko. On top of that, possess Sena-chan's body and enjoy the Sena-chan's body that she developed. Still, Sena loves the "prince" who is kind to her.